1. Field of the Invention
This invention relates to a chlorosilicate phosphor, and more particularly to a divalent europium activated strontium beryllium chlorosilicate phosphor.
2. Description of the Prior Art
British Pat. No. 1,087,655 and "Journal of Luminescence 3 (1971), 467-476" disclose a divalent europium activated strontium chlorosilicate phosphor [(Sr,Eu.sup.2+).sub.4 Si.sub.3 O.sub.8 Cl.sub.4 ] as one of chlorosilicate phosphors. The (Sr,Eu.sup.2+).sub.4 Si.sub.3 O.sub.8 Cl.sub.4 phosphor emits blue-green light of high luminance under excitation by ultraviolet rays, vacuum ultraviolet rays (xenon resonance line of 147nm), cathode rays, etc. Especially, as the emission efficiency of the phosphor under excitation by ultraviolet rays is markedly high even in a higher temperature range, the phosphor has been used as a color rendering phosphor for high pressure mercury vapor lamps.
However, the emission peak of the above described (Sr,Eu.sup.2+).sub.4 Si.sub.3 O.sub.8 Cl.sub.4 phosphor cannot be shifted from the wavelength of about 490nm, that is, the color of the light emitted thereby cannot be varied, which reduces the value of the (Sr,Eu.sup.2+).sub.4 Si.sub.3 O.sub.8 Cl.sub.4 phosphor as a color rendering phosphor.